* {
    margin: 0;
    padding: 0;
    list-style: none;
    box-sizing: border-box;
}

.container {
    width: 440px;
    position: absolute;
    left: 50%;
    top: 100px;
    transform: translateX(-50%);
    padding: 20px;
    /* height: 1000px; */
}

ul li {
    float: left;
    width: 100px;
    height: 40px;
    line-height: 40px;
    text-align: center;
    border: 1px solid #ccc;
    margin-top: -1px;
    margin-left: -1px;
}

ul:nth-child(1) li {
    background-color: skyblue;
}

button {
    width: 40px;
    text-align: center;
}

.reset {
    margin-right: 5px;
}

.mask {
    width: 100%;
    height: 800px;
    background: rgba(0, 0, 0, .3);
    position: relative;
    padding-top: 200px;
    display: none;
}

.mask .box {
    padding: 20px;
    width: 300px;
    background-color: #fff;
    margin: 0 auto;
    text-align: center;
}

.add {
    width: 60px;
    padding: 5px;
    position: absolute;
    bottom: -30px;
    left: 50%;
    transform: translateX(135px);
}